1. Field of the Invention
The present invention relates to biodisintegrable thermoplastic resin moldings and to a process for producing same. More particularly, the present invention relates to biodisintegrable thermoplastic resin moldings comprised of a thermoplastic aliphatic polyester as a matrix resin having another type of thermoplastic resin uniformly dispersed therein and to a process for producing the resin moldings which comprises extruding a melt-kneaded mixture of the thermoplastic aliphatic polyester resin and another type of thermoplastic resin through a die under specific conditions.
2. Description of the Prior Art
In connection with the treatment of waste goods, a movement of prohibiting or limiting the use of plastics as packaging materials is being encouraged in recent years in Europe and America. In particular, biodisintegrable plastics wherein plastics are incorporated with starch are now put into practice in U.S.A. The disintegration of plastics in this case is attained by chemical decomposition of starch in the plastics by the action of microorganisms. In case the amount of starch incorporated into the plastics is small, however, the desired disintegration will not take place. On the other hand, if the amount of starch is large, the disintegration of the plastics will certainly take place, but the incorporated starch is granular and devoid of any plasticity so that the resultant resin products such as resinous sheets are significantly inferior in mechanical properties and secondary processability, such as thermoformability (in vacuum forming, pressure forming, matched die forming, etc.) into containers or the like products, to ordinary plastics containing no starch. Further, the use of such biodisintegrable plastics is limited only for the manufacture of films or bags where a secondary processing treatment is not required so such.
Anyway, all of the known conventional biodisintegrable resins are unsatisfactory in maintaining mechanical properties inherent to the pure resin components and are hardly processed to manufacture shaped articles.
Under the above circumstances, there is a great demand for developing new type biodisintegrable plastics which enable disintegration by microorganisms and prevent deterioration in mechanical properties and thermoformability by incorporation of a substance chemically decomposable by microorganisms.